Chromatography columns are generally formed of three basic components, a column body, typically in the form of a hollow cylinder; a bottom plate which seals off the bottom of the column and which typically includes an outlet from the column bottom and a top plate. At least one plate is movable within the column. Typically it is the top plate that is designed to move within the interior of the column body and seal against the inner walls when in place. Between the bottom and top plates one places a media used to remove the desired components from a fluid stream. The top plate is moved to be against the top of the media and often is used to slightly compress the media to form a fixed bed. The outer edge of the top plate contains a seal that forms a liquid tight seal between the top plate and the inner wall of the body so that no fluid escapes. It also contains an inlet into the space between the top and bottom plates. Both plates also have a screen or frit that is closest to the media so as to separate the inlet and the outlet from the media itself and to act as a flow distributor to help ensure even flow of the fluid through the bed of media.
The seal on the movable plate has been one of two designs. The first is an inflatable seal that, once the plate is in the desired position, is inflated with compressed air to expand the seal and form a liquid tight arrangement between the inner wall and the plate. When it is desired to move the plate, the pneumatic or hydraulic supply is removed and the seal deflates so as to allow room between the inner wall and the seal. This clearance is enough to allow the plate to move unhindered see U.S. Pat. No. 6,139,732 for example.
Problems with such seals are many. If the air or hydraulic supply is cut off during use of the column, the seal deflates and the bed is disturbed with loss of fluid around the deflated seal. Not only is the batch ruined (with the loss of product), the column now must be taken apart and sanitized and repacked before it can be restarted.
Additionally, the seals being elastomeric and inflatable are by their nature semipermeable and tend to lose air to the bed over time. This introduces air into an otherwise closed environment and reduces the efficiency of the column by blocking certain areas of the bed from fluid flow and/or drying out the media (rendering it inactive). For hydraulic pressurized seals there is a concern that in the event of rupturing the hydraulic fluid may cause contamination.
Lastly, if the air or hydraulic pressure is not properly regulated, the seal can be overinflated and caused to tear or burst.
The other alternative is to position the seal above the flow distributor and have a second plate portion located above the seal. The flow distributor and second plate portion are capable of moving relative to each other by a series of threaded rods. In the unsealed position, they are at a position furthest from each other. Once the flow distributor is at the desired position, the two pieces are moved relative to each other to compress the seal between them, causing it to expand outward and form a liquid tight seal with the inner wall. Typically, this is arranged by moving the second plate piece toward the flow distributor see U.S. Pat. No. 6,132,605 and EP 3476996 A2 for example.
Seals of this type are slow to activate and deactivate. Moreover, they can be easily over-compressed causing damage to the seal and other column components. What is desired is a seal that can have infinite adjustability so that it is not over compressed and can be set such that it is possible to dynamically adjust the seal in a longitudinal direction (that is to move the top plate while retaining a degree of sealing.) (As maybe required for certain packing operations).
Additionally, as relative motion between the two components is the force for creating the seal it has been found that the flow distributor often is moved away from the bed creating a gap which disturbs the flow characteristics of the column.
A preferred embodiment would be to have a single point for actuation of the seal which is both more convenient and less prone to manual error than having multiple points of actuation equi-spaced about the circumference as is taught by the existing art. However when the diameter of the column is in excess of 20 cm, it becomes increasingly difficult to engineer a single point manual actuation of the seal.
What is needed is a sealing device that is easily activated and deactivated and which is an improvement over the existing seals. The present invention is just such a device.